# force numbers to strings before printing:
$ perl -wMstrict -le 'print "".1e-3; print "".0.001;
    print "".0.0_0_1; print "".0x1.0624dd2f1a9fcp-10'
0.001
0.001
0.001
0.001
# edited for brevity:
$ perl -wMstrict -MDevel::Peek -le 'Dump( 1e-3 )'
  NV = 0.001
$ perl -wMstrict -MDevel::Peek -le 'Dump( 0.001 )'
  NV = 0.001
$ perl -wMstrict -MDevel::Peek -le 'Dump( 0.0_0_1 )'
  NV = 0.001
$ perl -wMstrict -MDevel::Peek -le 'Dump( 0x1.0624dd2f1a9fcp-10 )'
  NV = 0.001

##</code><code>##

$ perl -wMstrict -le '
    if ( sprintf("%.3f",0.001) eq sprintf("%.3f",0.001001) )
      { print "yes" } else { print "no" }'
yes